A digital copying machine as an example commercialized image forming apparatus produces a copy of an original image in the following manner. First, the original image is read by means of an image reading section. Then, the document image as read is subjected to the image processing function as specified, and the resulting image data are printed out by a recording section. In the digital copying machine, an image can be formed on the sheet by utilizing the image processing function of the digital copying machine.
On the other hand, an idea of constituting a network by interconnecting a plurality of image recording apparatuses or the like has been proposed. For example, Japanese Unexamined Patent Application No. 116834/1978 (Tokukaisho 53-116834) discloses an arrangement wherein a plurality of image reading apparatuses and a plurality of image recording apparatuses are connected by a single control section.
According to the described arrangement, a copy of an original image as read by any one of the plurality of image reading apparatuses is printed out by any one of the plurality of image recording apparatuses. This arrangement reduces a stand-by time of the image-reading apparatus required for carrying out such processes as a replacement of an original document in the image-reading apparatus, etc.
Japanese Unexamined Patent Application No. 198958/1986 (Tokukaisho 61-198958) discloses an image forming system wherein a plurality of copying machines including an image reading section and an image recording section are connected by a control device. In the image forming system, according to a document copy mode as set, an image signal to be recorded is distributed into a plurality of copying machines, and a copying operation is performed parallelly in the plurality of copying machines.
Japanese Unexamined Patent Publication No. 285977/1989 (Tokukaihei 1-285977) discloses an image processing section including determination means for determining if a copying of image data as read by an image reading section is permitted, i.e., if a duplication of the document image is prohibited, and has a function of controlling a copy output based on an output from the determination means when processing the document image.
However, the described conventional image forming systems have drawbacks in that a document image which is prohibited to be formed or processed cannot be prevented effectively.
For example, in the conventional digital copying machine, the determination means for determining if a copying of the image is permitted is incorporated in an image processing machine. The determination means basically has such a function that copy-prohibited data such as marketable securities, etc., are stored in a unit beforehand, and the determination of the image is carried out by collating the document image data with the copy-prohibited data as stored. In the described arrangement, as the unit is fixed in the digital copying machine, the data may be damaged as being stored for a long time within the unit, which causes an erroneous result when determining if the document is permitted to be copied.
Additionally, in the described digital copying machine provided with the determination means, a control of the copy-prohibited document image as processed is permitted; however, the copy-prohibited document can be copied by other image processing apparatus which is not provided with the determination means.
Furthermore, even after a new image processing apparatus provided with determination means of a higher level becomes available in the market with an increase in an amount of data or an improvement in algorithm, a determination still has to be carried out by the existing determination means of the image processing apparatus. For this reason, in the case where the determination means of a desired level is not provided in the digital copying machine of one's possession, or a digital copying machine provided with the determination means of a higher level becomes available in the market, the user is required to purchase a new digital copying machine only for obtaining the determination function of a higher level or improving the precision of the result of determination.